Any doc reference on /entropy file ?

[Daniel Bye]

On Tue, Dec 16, 2008 at 02:08:10PM +0100, Bernard Dugas wrote:
> Hi,
> 
> When i look at / in a standard installation like :
> FreeBSD XXX 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sun Feb 24 19:59:52 UTC 
> 2008     root at logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
> 
> There is only 1 file, named entropy :
> 
> -rw-------   1 root  wheel  4096 Dec 11 17:36 entropy
> 
> I can't find any reference to that file in FreeBSD doc.
> 
> Any reference to it ? What is it used for ? I have look in RANDOM area, 
> but no reference...
> 
> Do i have to keep it read/write ? Can i put it in /var instead of / to 
> be able to keep / read-only ?

It is used to safely seed the random number generator, I believe.

A quick search through /etc/rc.d/* and /etc/defaults/rc.conf reveals
that you can set $entropy_file in /etc/rc.conf to anything you like, 
although a comment suggests

  # Set to NO to disable caching entropy through reboots.
  # /var/db/entropy-file is preferred if / is not avail.

So yes, it seems you could move it off / if you want.

Dan

-- 
Daniel Bye
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